From now on we shall always assume that a kernel \(\kappa \)  is pseudo-positive [1]}, which means that \(\kappa (\mu ,\mu )\geqslant 0\)  for all \(\mu \in \mathfrak {M}^+\)  (or equivalently, for all \(\mu \in \mathfrak {M}^+\)  of compact support, cf. Lemma REF ). A (pseudo-positive) kernel \(\kappa \)  is said to be strictly pseudo-positive if \(\kappa (\mu ,\mu )>0\)  for all \(\mu \in \mathfrak {M}^+\) , \(\mu \ne 0\) , of compact support.
